Refrigeration



REFRIGERATION Filed Feb. 26. 1945 Fial,

. [18 AIR FLOW l 59 Al& FLOW U Snventor Henry B.Powna1l.

] (Ittornegs Patented Mar. 14. 1944 UNITED STATES PATENT OFF-ICE 2,344,214 REFRIGERATION Henry B. Pownall, York, Pa., as'signor to Corporation, a corporation of Delaware York Application February 26, 1943, Serial No. 477,242

' 8 Claims. (01. 62-115) -of vaporous refrigerant leaving the evaporator.

They operate to control the rate of supply of refrigerant to the evaporator in su h a way that the vapor leaving the evaporator is always superheated.

Normally there are only two sources of heat for superheating this vapor. The first source is the medium cooled by the evaporator. The second source is the liquid refrigerant entering the evaporator. When such a control is applied to a low temperature system, the available heat is v insu-fllcient to give a degree of superheat great enough to assure precise control of the valve.

The present invention in its broadest aspects contemplates the supply of heat to vaporous re-' frigerant leaving the evaporator and before the" refrigerant afiects the thermal bulb, such heat being supplied at a substantially uniform rate and being heat additional to that which may be derived from either of the two sources above named.

While the widest latitude is possible in theselection of the source of heat, it is desirable to use waste heat from the refrigerative circuit, This can be done in various ways. While the invention can be applied to simple circuits, it .is chiefly valuable in low temperature refrigeration. Most low temperature circuits are either of the cascade type or of the compound type. Since the invention can be applied very effectively to circuits of these two types, it will be described as so embodied, without, however, implying any neces: sary limitation to either of these two arrangements.

In the drawing which is largely diagrammati Fig. 1 shows a compound system.

Fig. 2 is a similar view showing a cascade system. I v

' In 1 the low stage. compressor appears at 6. Its discharge is connected through the interstage connection 1 with the intake of the high s a e compressor 8. Compressor 8 discharges" through the hot gas line 9 into the condenser II from which liquid refrigerant flows by gravity to the receiver l2. From the receiver l2 the liquid line H leads through the zig-zag tube ll of the expansion cooler whose shell is indicated at I5. Liquid refrigerant cooled by passage through the coil l4 flows through the expansion valve I6- and connection 11 to the evaporator I 8 which is here assumed to be a low temperature evaporator. From the evaporator l8 a suction connection [9 leads through the tubes 2| in the shell 22 of the super-heater.

Refrigerant vapor superheated by passage I through the tubes 2| flows through the suction to the space refrigerant flowing to the low ,.,bulb:3 l which is shown line 23 to the intake ofthe low stage compressor 7 6. A branch 24 leads from the liquid line I:

to the space within shell 22 around the tubes 2|.

From this space a line 25 leads to the expansion valve 26 which controls the flow of refrigerant within the expansion cooler l5 around the tube l4. From the shell of the expansion cooler l5 a line 21 leads to the interstage connection 7. Expansion valve l6 has a regulatory thermal bulb 28 which is mounted on the suction connection 23 and is connected with expansion valve 16 by the capillary 29. Thus the bulb is subject to the temperature of the stage compressor 6 after being superheated by passage through the tubes 2|.

Expansion valve 26 has a regulatory thermal so located as to be subject the interstage connection 1 beyond its junction with the line' 27. The bulb 3| isconnected with the valve 26 by the capillary 32. It willbe observed that the direct expansion cooler in shell I5 is to temperature in and thus superheats that vapor-before it reacts upon the thermal bulb 28. Thisimproves the regulatory performance of the expansion valve i6 and at the same time penalizes the system to the least degree practicable. It must be remembered that accurate control of the valve 18 is so important that it may be sought even at .the sacrifice of some theoretical efliciency.

The cascade system shown in Fig. 2 is quite similar in its ul imate function. In the cascade in effect a subordinate evaporator in which the suction pressure is 45 of the superheater,

through the suction line 52 to plied to two system there are two refrigerative circuits, one operating in a relatively high and the other in a relatively low temperature range. These circuits are normally interconnected to the extent that the evaporator of the high temperature circuit and the condenser of the low temperature circuit are combined in one surface heat exchanger.

According to the present invention, the two circuits are further related by the interposition of the superheater in which warm liquid refrigerant flowing from the condenser of the high' temperature circuit exchanges heat with cold vaporous refrigerant evaporator ofthe low temperature circuit.

In Fig. 2 the compressor of the high temperature circuit is indicated at 4| and discharges through a hot gas line 42 to a condenser 43 from which the liquid line 44 leads through the shell the flow being around the tubes 46 within the shell and thence to connection 41 which leads to the expansion valve 48. The expansion valve 48 controls delivery of liquid refrigerant to the space within the tubes 4! within the shell SI of the heat exchanger. From the tubes 49 evaporated refrigerant flows the intake of compressor 4!. The expansion valve 48 is of the superheat controlled type and includes a thermal bulb 53 which is connected with the valve by capillary 54 so as to participate in the control of the valve 48. The compressor temperature circuit is indicated at charges through the hot gas line it into the space within the shell around the tubes 4!. Compressed refrigerant is condensed in this shell and flows by way of line 51 to the main expansion valve 58. From the expansion valve 58 refrigerant flows to the main evaporator 69. From the evaporator 59 a suction line 81 leads to the entrance end of the tubes 48 within the superheater shell 45. From the discharge end of the tube 46 the superheated refrigerant flows by line 62 from theintake to compressor 55. Expansion valve 58 is of the superheat controlled type and includes a thermal bulb 63 subject to the temperature of vaporous refrigerant flowing through the line 62. The bulb .3 is connected with the valve 58 by the usual capillary.

Here again superheat is added to vapor leaving the main evaporator and is heat additional to that derived from the medium cooled by the evaporator 59 and additional to any heat which might be derived from liquid refrigerant fed to the evaporator 59.

In the embodiment of Fig. 2, the refrigerative circuits are distinct except that they exchange heat at two points. The action is similar to liquid which flows evaporated to cool to the main evaporator.

While the invention has been described as aptypical circuits using more than one compressor, this is intended to illustrate the best known ways of applying the invention to those circuits which are commonly used for low temperature refrigeration.

The invention is not limited to use in either of the systems illustrated, for in its broadest aspects it involves a supply of superheat to vapor leaving. the main evaporator, the heat so supplied being additional to heat derived from the medium cooled by the evaporator and from liquid refrigerant flowing to the evaporator. Obviously flowing from the .this broad idea can be applied to a simple circuit in various ways.

What is claimed is: 1. The combination of a refrigerative circuit 5 including an evaporator to which refrigerant is delivered in the liquid phase-and from which refrigerant is withdrawn in the vapor phase; and means for delivering at a substantially uniform rate to the oil-flowing vapor to superheat the in latter, heat additional to that derived from the medium cooled by the evaporator and from a source external to the circuit through the evaporator.

2. The combinationof a refrigerative circuit including an evaporator to which refrigerant is delivered in the liquid phase and fromwhich refrigerant is withdrawn in the vapor phase; an expansion valve of the superheat control type regulating the delivery of liquid refrigerant to go the evaporator and including a heat sensitive controlling element subject to the temperature of off-flowing vaporous refrigerant beyond the evaporator; and means for delivering at a substantially uniform rate to the off-flowing vapor, before the vapor reacts upon said sensitive element, heat additional to that derived from the medium cooled by the evaporator and from a source external to the circuit through the evaporator.

3. A refrigerative system of the compressor, condenser, evaporator circuit type having refri erant paths which are distinct at least to the extent that there are two evaporators and dis- -tinct connections for delivering liquid refrigerant to, and for withdrawing vaporous refrigerant from, respective evaporators; and heat exchang-.

ing means for delivering heat from liquid refri erant flowing to one of said evaporators to the cold vaporous refrigerant flowing from the other of said evaporators.

4. A refrigerative system of the compressor, condenser, evaporator circuit type having refrigerant paths which are distinct, at least to the extent that there are two evaporators each with its own connections for supplying liquid refrigerant and withdrawing vaporous refrigerant, one of said evaporators being the main evaporator which carries the refrigerative load and operates at a low temperature, and the other evaporator operating at a higher temperature and serving to abstract heat from liquid refrigerant to be S pplied to the main evaporator; and heat exchanging means serving to deliver heat from liquid refrigerant flowing to said other evaporator, to cold vaporous refrigerant flowing from the main evaporator.

5. The combination of two refrigerative circuits each of the compressor, condenser, evaporator circuit type, the second operating in a lower temperature range than the first. said circuits exchanging heat through two surface interchangers, one of which interchangers serves as the evaporator of the first circuit and the condenser of the second circuit, and the second of which exchangers transfers heat from the warm liquid refrigerant of the first circuit to cold vapor leaving the evaporator of the second.

6. The combination of two refrigerative circuits each of the compressor, condenser, evaporator circult type, the second operating in a lower temperature range than the first, said circuits exchanging heat through two surface interchangers, one of which interchangers serves as the evaporator of the first circuit and the 7s condenser of the second circuit, and the second ture of refrigerant of which exchangers transfers heat from the warm liquid refrigerant of the first circuit to cold vapor leaving the evaporator of the second;

an expansion valve in the secondicircuit controlling delivery of liquid refrigerant to the evaporator; and thermostatic means subject to temperain the second circuit beyond the second heat exchanger, and exercising a controlling eflect on the expansion valve. '7. A refrigerative circuit comprising compres- .sors connected in stages; a condenser to which the high stage compressor delivers; an evaporator fed from the condenser; a suction connection from the evaporator to the intake of the low stage compressor; a surface cooler interposed in the flow path from the condenser to the evaporator and having expansion coolin means ccn nected with an lnterstage compressor connection and with a branch liquid supply connection from the condenser; and a surface heat exchanger interposed in said branch connection and in thesuction connection between the evaporator and low stage compressor.

sors connected in stages:

. the flow path from and the low-stage compressor.

HENRY B. POWNALL.

. '3 8. A refrigerative circuit comprising compresa condenser'to which the high stage compressor delivers; an evaporator fed from the condenser; a suction connection from the evaporator to the intake of the low stage compressor; a surface cooler interposed in the condenser to the evaporator and having expansion cooling means connected with an interstagecompressor connection and with a branch liquid supply connection from c the condenser; a surface heat exchanger interposed in said branch connection and in the suction connection between the evaporator and low stage compressor; and an expansion valve of the superheat controlv type interposed .between the surface cooler and-the evaporator and including a thermal element for controlling the valve, subject to the temperature of refrigerant in the suction connection between the heat exchanger 

